Angular position measuring devices, also referred to as shaft encoders, are used for measuring rotary motions of a rotationally mounted member, e.g., a shaft, over one or more revolutions (multiturn functioning). In so doing, the rotary motion is recorded incrementally or absolutely. In conjunction with gear racks and gear wheels or with threaded spindles, linear motions can also be measured by an angular position measuring device.
In order to adjust alignment errors, for example, between the shaft of an angular position measuring device and the shaft to be measured, couplings are frequently used. The shaft of the angular position measuring device can then be fitted rigidly to the shaft to be measured. The coupling compensates for the axial and radial relative motions between the shaft to be measured and the measuring unit of the coupling, and it reduces the forces generated thereby. So that the measuring results are not corrupted, the respective coupling should behave in a manner that is rigid or torsion resistant.
A coupling is described in PCT International Published Patent Application No. WO 01/02808 that has four links or tabs which are each offset by 90°. In this context, two opposite links that are aligned in parallel are each fastened to the same component part. This arrangement is believed to have the disadvantage that, among other things, the respective coupling may require a great deal of space comparatively speaking, for angular position measuring devices having large shaft diameters (e.g., for those having hollow shafts for accommodating a shaft that is to be measured).